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Lab Manual - Upper GI Tract |
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Assignments:
- Before lab:
- Complete the learning module entitled Autonomics of the Head & Neck.
- Download and review the Lab Overview PowerPoint.
- Review the Prelab Learning Module for the upper GI tract.
- Review the Steps of Dissection and Dissection Videos.
- During lab:
- Follow the steps of the dissection procedure in the Lab Manual (this page).
- Be certain to identify all of the Review Items.
- After lab:
- Read the Dissector Answers to cover the Learning Objectives for this lab.
- Read the Clinical Case for this lab.
- Review the Practice Questions for this lab.
Learning Objectives:
Upon completion of this session, the student will be able to:
- Describe the hard and soft palate.
- Describe the location of the parotid salivary gland.
- Identify three main neurovascular structures that traverse the parotid gland.
- Identify the branches of the facial nerve in the face.
- Identify some exemplary muscles of facial expression acting on the oral opening.
- Identify the masticatory muscles and give their functions.
- Define the boundaries and contents of the infratemporal fossa.
- Identify the branches of the trigeminal nerve and their functions related to mastication and sensation from the face.
- Identify the chorda tympani nerve and give its function.
- Describe the structure and function of the temporomandibular joint.
- Identify the muscles bordering the submandibular and paralingual spaces.
- List and identify the major nerves and vessels of the submandibular and paralingual spaces.
- Describe the submandibular and sublingual salivary glands and give their innervations.
- Describe the muscles of the tongue.
- Describe the oral cavity, its oral vestibule, and the dental arches (including temporary and permanent dentitions).
- Review the carotid sheath and contents.
- Identify, trace and describe the general functions of cranial nerves IX (glossopharyngeal), X (vagus), XI (spinal accessory), XII (hypoglossal).
- Describe the pharynx, its anatomical architecture and action of its musculature during swallowing.
Procedure:
1. Review the relevant osteology of the skull and mandible. (Play movie; View images: N 2, 4, 8, 15, 123, TG 7-03, 7-04A, 7-06, 7-32B, 7-32C, 7-57, 7-87)
Locate on the skeleton or palpate: the zygomatic arch (zygoma), external acoustic meatus (bony and cartilaginous), mastoid process, styloid process, stylomastoid foramen, ramus, posterior border, angle, body, mental foramen, and symphysis of mandible; rim of orbit, supraorbital notch or foramen, and infraorbital foramen.
2. Examine the muscles of the soft palate. (Play movie; View images: N 37A, 37B, 37C, 63, 64, 52, 63, 64A, 64B, 68, 69, TG 7-06, 7-22, 7-23, 7-24, 7-39, 7-67)
In the roof of the mouth identify the soft palate, uvula, hard palate; palpate the hamulus of the medial pterygoid plate.
In the nasopharynx identify: opening of auditory tube, torus tubarius, pharyngeal tonsil and pharyngeal recess.
Expose the levator veli palatini muscle. Find the tensor veli palatini muscle anterior and deep to the levator veli palatini and then expose its insertion by removing the mucous membrane from the inferior surface of the soft palate. Note its relationships to the hamulus and the palatine aponeurosis. What is the primary function of the tensor veli palatini?
3. Remove the skin of the face except for eyelids and nose. (Play movie; View images: N 24, 31, 32, TG 7-13, 7-15, 7-36, 7-75)
Skin the face from the inferior border of the mandible to several centimeters above the zygomatic arch, and from the mastoid process to the anterior mid-line (exclusive of the eyelids and nose, which will be done later). Trace the great auricular nerve to its distribution to the skin over the angle of the mandible.
4. Expose the parotid gland and its duct, carefully dissecting the branches of the facial nerve passing through it. (Play movie; View images: N 23, 24, 25A, 25B, 46, 51, 54, 69, 70, 122, 123, 125, TG 7-19, 7-31A, 7-31B, 7-35, 7-36, 7-38, 7-71, 7-72, 7-73, 7-75, 7-81, 7-84, 7-87, 7-89)
Remove the subcutaneous fat overlying the parotid gland and expose the deep fascia covering the gland. This is the parotid fascia (parotideo-masseteric). Remove this fascia from the superficial surface of the gland, but do not cut around the borders of the gland with a scalpel. Using a probe, begin at the top of the gland and carefully dissect along its borders for nerves and other structures that emerge from them. Identify: auriculotemporal nerve, superficial temporal artery and vein, parotid duct, and the temporal, zygomatic, buccal, (marginal) mandibular and cervical branches of the facial nerve.
5. Identify the branches of the facial nerve within the parotid gland. (Play movie; View images: N 13, 25, 27, 28, 123, TG 7-09, 7-12, 7-16, 7-31, 7-87)
Follow the branches of the facial nerve into the substance of the parotid gland, carefully removing the gland tissue from around these branches. Trace the facial nerve to the stylomastoid foramen, and observe that it passes lateral to the retromandibular vein and external carotid artery. Identify the temporofacial division of the facial nerve, giving temporal, zygomatic, and buccal branches, and the cervicofacial division of the facial nerve with its buccal, (marginal) mandibular, and cervical branches.
6. Identify the retromandibular vein and its divisions and review the branches of the external carotid artery to the face region. (Play movie; View images: N 23, 61, 69A, 69B, 70, 71, TG 7-19, 7-20, 7-31, 7-35, 7-71, 7-72, 7-73)
Next, dissect the parotid gland free from the anterior border of the sternocleidomastoid muscle and palpate the styloid process, which is deep to the gland. Identify the posterior belly of the digastric muscle and the stylohyoid muscle. Find the anterior and posterior divisions of the retromandibular vein emerging from the gland. The anterior division unites with the facial vein to form the common facial vein, while the posterior division of retromandibular vein unites with the posterior auricular vein to form the external jugular vein. While identifying the stylohyoid muscle, look for the external carotid artery that is curving around the muscle to penetrate into the parotid fossa and gland.
Trace the external carotid artery to its termination and review or find the following branches: superior thyroid, ascending pharyngeal, lingual, facial, occipital, and superficial temporal. The maxillary artery, an important branch of the external carotid, will be seen when the infratemporal fossa is studied.
Angiogram of the head and neck 7. Clean and identify the muscles of facial expression related to the mouth. (Play movie; View images: N 23, 26, 54A, 54B, 69, 70, 123, TG 7-19, 7-30, 7-31, 7-35, 7-71, 7-72, 7-73, 7-87)
The muscles of facial expression are innervated by branches of the facial nerve (CN VII). They lie primarily within the subcutaneous tissue, surround natural orifices (mouth, nose, orbit, ear) and provide a variety of facial expressions. They originate from bone or fascia, but insert into the skin. Review the general arrangement of the muscles in your atlas, but dissect only the following which act on the oral opening: zygomaticus major, levator labii superioris, levator anguli oris, depressor anguli oris, depressor labii inferioris, and orbicularis oris. On one side only, expose the buccinator, which is the deepest of the facial muscles, and main muscle of the cheek. Note the buccal fat pad interposed between the buccinator and the masseter muscle. As the facial muscles are exposed, trace the facial artery and vein past the lips and toward the medial angle of the eye.
Surface anatomy of the face 8. Review the osteology of the infratemporal fossa and oral cavity. (Play movie; View images: N 4A, 4B, 6, 8, 11, 12, 13A, 13B, 14, TG 7-04, 7-06, 7-07, 7-08, 7-32A, 7-32B, 7-32C)
On the skull, identify the articular eminence, mandibular fossa, lateral and medial pterygoid plates, pterygomaxillary fissure, foramen ovale, foramen spinosum and styloid process. On the mandible, identify the mandibular notch, coronoid process, condyle, pterygoid fovea, neck, lingula, mandibular foramen, mylohyoid line, and mental spines.
9. On the right side, reflect the masseter and zygomatic arch downward toward the angle of the mandible. (Play movie; View images: N 15, 23, 24, 25, 46, 54A, 54B, 69, 70, TG 7-31A, 7-31B, 7-32B, 7-32C, 7-34, 7-35, 7-36, 7-71, 7-73, 7-75, 7-84)
On the right side of the head, make a vertical incision through the parotid gland and turn it forward, detaching it from the masseter muscle. The incision should parallel the posterior border of the ramus of the mandible. Observe the cut facial nerve and the retromandibular vein within the gland.
Skin the temporal fossa and expose the temporal fascia. Review the superficial temporal artery and vein and the auriculotemporal nerve (V3). Completely remove the temporal fascia and clean the temporalis muscle noting different directions of the muscle fibers. Locate and trace the buccal nerve (V3) as it passes through the inserting fibers of temporalis to distribute to the skin of the cheek and oral mucosa.
Below the zygomatic arch, clean the masseter muscle. Cut the zygomatic arch by sawing through it just in front of the articular eminence and as far forward as possible on the zygomatic bone. Reflect the masseter and arch together toward the angle of the mandible. Locate the nerve to masseter emerging through the mandibular notch and cut it as you reflect the masseter inferiorly.
Now, saw through the base of the coronoid process and reflect all of the temporalis muscle upward. Can you find the anterior and posterior deep temporal nerves and arteries?
10. Remove the ramus of the mandible by sawing through the neck of the condyle and clipping the ramus above the mandibular foramen. (Play movie; View images: N 15, 46, N55, TG 7-32B, 7-32C, 7-34, 7-37)
Next, to get access to the infratemporal fossa, saw through the base of the neck of the condyle. Then, use the bone clippers to carefully remove the mandibular ramus down to the mandibular foramen, taking care to identify and preserve the inferior alveolar neurovascular bundle entering the mandibular foramen. Continue to preserve the inferior alveolar neurovascular bundle as the entire ramus of the mandible is removed down to the angle.
11. Clean the lateral and medial pterygoid muscles, examine the temporomandibular joint, remove the condyle of the mandible and lateral pterygoid muscle to expose the branches of the trigeminal nerve and the maxillary artery. (Play movie; View images: N 4, 15, 16A, 16B, 46A, N46B, N53, 55, 69, 70, 125, 133, TG 7-06, 7-32A, 7-32B, 7-32C, 7-34, 7-35, 7-36, 7-37, 7-73, 7-84, 7-90)
Clean the lateral pterygoid muscle. Note its two heads and different attachments. While cleaning it, carefully expose the maxillary artery and define its course (is it superficial or deep to the muscle?).
Examine the temporomandibular joint (TMJ) by cutting its capsule open. Identify the articular disk and the two articular compartments. What is the articular eminence? Consider the condylar movements at each compartment. Note the attachment of the upper head of the lateral pterygoid muscle to the disc and the lower head to the pterygoid fovea of the mandible. Now, completely remove the condyle and neck with the attached disc and lateral pterygoid muscle. Examine the disc and note its shape, thickness and attachment of the upper head. Examine the mandibular condyle, and note depth of of the mandibular fossa. If the maxillary artery courses deep to lateral pterygoid muscle, you will now be able to clean it fully.
Motion at the temporomandibular joint Trace the maxillary artery toward the pterygomaxillary fissure. Identify the middle meningeal, inferior alveolar, buccal, and muscular branches to masseter, temporalis, and medial and lateral pterygoid muscles. Remove the pterygoid plexus of veins and note the maxillary vein.
Identify the lingual and inferior alveolar nerves and trace them toward the foramen ovale. Identify the auriculotemporal nerve passing medial to the mandibular fossa. Note the chorda tympani joining the lingual nerve from behind. What kind(s) of fibers does it carry? Identify other branches of the mandibular division of the trigeminal, a mixed motor and sensory nerve. Accompanying autonomic fibers? Otic ganglion?
Clean the lateral surface of the medial pterygoid muscle and review its attachments.
Muscles of the infratemporal fossa 12. Clear the deep cervical fascia and expose the submandibular gland, the digastric, and mylohyoid muscles and facial artery. (Play movie; View images: N 24, 27, 28, 46, 53A, 53C, 59, 61, 63, 69, 70, 71, TG 7-12, 7-17, 7-18, 7-19, 7-31, 7-34, 7-35, 7-37A, 7-37B, 7-40A, 7-40B)
On both sides of the face, define the boundaries of the submandibular triangle. Clear the superficial layer of deep cervical fascia and expose the submandibular gland, the digastric muscle (its anterior and posterior bellies), the mylohyoid muscle and the stylohyoid muscle.
Surface structures of the oral cavity Teeth Muscles of the oral cavity Trace the facial artery and vein in the neck, noting relations with the submandibular gland (which one is superficial or deep to the gland?). Locate the mylohyoid nerve (what muscles does it supply; what does it arise from?).
Examine the submandibular gland, its extent within the submandibular triangle and its deep part that hooks around the posterior border of the mylohyoid muscle.
On the right side only, carefully sever the insertion of the stylohyoid muscle and the attachment of the digastric tendon from the hyoid bone and reflect these muscles. Note the hypoglossal nerve and its vena comitans passing deep to the posterior border of the mylohoid muscle. Now sever the origin of the mylohyoid muscle from the mandible and reflect it down toward the hyoid bone. Identify the hyoglossus muscle and trace it from its hyoid bone origin into the tongue. Now identify the lingual artery at its origin from the external carotid artery, and trace it until it passes deep to the hyoglossus muscle to supply the tongue.
13. On the left side of the head, incise the mucous membrane of the floor of the mouth to expose the paralingual space. (Play movie; View images: N 51A, 51B, 58, TG 7-37, 7-38B, 7-38C)
Incise the mucous membrane of the floor of the mouth next to the tongue, being careful to not cut too deeply. Identify, but don't cut, the palatoglossal fold. Carefully reflect the mucous membrane laterally to expose the contents of the paralingual space.
14. Examine the sublingual gland, the lingual and hypoglossal nerves, the submandibular ganglion and submandibular duct. (Play movie; View images: N 46, 51, 53, 59, 61, 69, 126, TG 7-37A, 7-37B, 7-38, 7-84, 7-88)
On the right side, incise the oral mucosa in the floor of the mouth and flip the mandible up to expose the paralingual space. Be careful not to cut the lingual nerve.
On both sides, identify the following structures:
- Sublingual gland, the smallest of the salivary glands.
- Submandibular duct courses anteriorly against the medial surface of the sublingual gland and opens onto the sublingual caruncle.
- Lingual nerve (V3), in the paralingual space, passes lateral and then inferior to the submandibular duct and has the submandibular ganglion (parasympathetic) attached to it.
- Deep portion of the submandibular gland, from which extends the submandibular duct.
- Hypoglossal nerve, the most inferiorly located element in the paralingual space.
15. Examine the tongue, identifying its parts, intrinsic and extrinsic muscles. (Play movie; View images: N 53A, 53C, 56, 57A, 57B, 58, 59, 62, 63, 68, 126, TG 7-20, 7-32, 7-38, 7-39A, 7-39B, 7-40, 7-94)
On the tongue identify the foramen cecum (significance? ), and the row of vallate papillae. Where is the lingual tonsil? Identify the extrinsic muscles of the tongue: genioglossus, hyoglossus, and styloglossus muscles. Consider the motor and sensory (special and general) innervation of the tongue. Read about the intrinsic muscles of the tongue. Consider actions of both groups of muscles in moving the tongue and changing the shape of the organ. Identify the geniohyoid muscle lying between the mylohyoid and the genioglossus muscles.
In the mouth, examine the gingiva (gums). Identify central and lateral incisors, canines, first and second premolars, and the first, second, and third molars, if present. What are deciduous teeth? Distinguish between oral cavity proper and the vestibule.
Skull structures Cranial structures 16. Review the osteology of the pharynx, larynx and hyoid bone. (Play movie; View images: N 4, 6, 8, 13, 77A, 77B, TG 7-06, 7-08, 7-09, 7-25, 7-28, 7-32)
On the base of a skull locate the following structures: pharyngeal tubercle, medial pterygoid plate, pterygoid hamulus. On the hyoid bone identify body, greater and lesser cornua (horns). Identify the thyroid cartilage, the cricoid cartilage and the arytenoid cartilage.
17. Clean the cervical sympathetic trunk, vagus nerve, carotid arteries and internal jugular vein. (Play movie; View images: N 8, 73, 75, 125A, 125B, 130, 131, TG 7-06, 7-14, 7-15, 7-20, 7-21, 7-71, 7-72, 7-90, 7-92, 7-95)
Clear the fascia of the carotid sheath from the contained nerves and vessels. These contents enter or exit the skull through the external opening of the carotid canal and the jugular foramen, and are located medially and dorsally (behind) the styloid process in a space referred to as the retrostyloid space.
Identify and trace each of the following:
- Cervical sympathetic trunk: superior cervical ganglion, branches to pharyngeal plexus, external carotid nerve and plexus, internal carotid nerve, and cardiac nerves.
- Vagus nerve: pharyngeal branch (anterior to internal carotid artery), superior laryngeal nerve, branches (medial to internal carotid artery), cardiac nerves.
- Internal jugular vein, receiving the pharyngeal plexus of veins
- Carotid bifurcation, the carotid sinus (body?), and the internal carotid artery
- External carotid artery and its first five branches: superior thyroid artery, ascending pharyngeal artery, lingual artery, facial artery, and occipital artery.
Do you find any lymph nodes (retropharyngeal)?
18. Identify and trace the glossopharyngeal, accessory, and hypoglossal nerves. (Play movie; View images: N 32, 67, 71A, 71B, 125, 127, 128, TG 7-17, 7-18, 7-20, 7-21, 7-90, 7-93, 7-94)
Identify and trace each of the following:
- Glossopharyngeal nerve: relations to stylopharyngeus muscle, branch to muscle, pharyngeal branch, carotid sinus nerve.
- Accessory nerve: relations to internal jugular vein and sternocleidomastoid muscle.
- Hypoglossal nerve: lateral to both external and internal carotid arteries.
19. Clean and identify the muscles of the pharynx and pharyngeal plexus. (Play movie; View images: N 13, 35, 67, 68, 77, 125, 126, 130, 131, TG 7-09, 7-10, 7-21, 7-25, 7-26, 7-90, 7-92)
Consider components of the pharyngeal plexus of nerves and the pharyngeal musculature. Carefully remove the buccopharyngeal fascia, the pharyngeal plexus of veins and any loose connective tissue overlying this musculature. Palpate and locate the greater horn of the hyoid bone and the superior horn of the thyroid cartilage. Define the three pharyngeal constrictor muscles (superior, middle, and inferior) and trace each as close to its origin as possible. Observe the pharyngobasilar fascia forming the pharyngeal wall above the superior pharyngeal constrictor. What tissue is it? Note the shape of the different parts of the pharynx. Clear the stylopharyngeus muscle and trace to the pharynx. Between what two muscles does it pass? Note the beginning of the esophagus, arrangement of musculature, and attachment. Consider the complete blood supply to pharyngeal constrictors. Innervation?
20. Examine the subdivisions of the pharynx, noting their features. (Play movie; View images: N 41, 62, 64, 66, 67, 69, 70, TG 7-22, 7-23AB, 7-23C, 7-39, 7-41)
Define nasal, oral and laryngeal portions of pharynx. What boundaries separate these regions?
Nasopharynx: Identify the choanae, soft palate and uvula, torus tubarius, pharyngeal recess, and the pharyngeal tonsil.
Oropharynx: Identify the palatoglossal and palatopharyngeal folds, tonsillar fossa, and palatine tonsil (if present). Remove one tonsil from its bed or fossa. What structures lie immediately deep (lateral) to it? Identify the glossopharyngeal nerve as it passes to the base of the tongue, inferior to the palatine tonsil. Where is the lingual tonsil? Identify the glossoepiglottic folds.
Laryngopharynx: Identify the epiglottis, which divides the oropharynx from the laryngopharynx, laryngeal inlet, piriform recesses and entrance to the esophagus.
Structures of the pharynx and larynx